Electric power steering apparatuses serving as vehicle steering apparatus assist drivers in steering by electric motors. More specifically, various types of sensors and others detect the steered states of steering members, for example, and control devices control electric motors based on the results of the detection of the steered states so that steering assist forces are applied to steering mechanisms.
It has been proposed that a control device is arranged between an electric motor and a speed reduction mechanism in an axial direction of the electric motor (see, e.g., Patent Documents 1 to 4).
An electric power steering apparatus that houses a control device at a position opposite to a speed reduction mechanism in an axial direction of a rotatable shaft in an electric motor within a case of the electric motor has been proposed (see, e.g., Patent Document 5).
An electric power steering apparatus in which a worm shaft in a speed reduction mechanism and a rotatable shaft in an electric motor are integrated with each other has been proposed (see, e.g., Patent Document 6).
In the electric power steering apparatus discussed in Patent Document 1, there is provided, between a motor housing in the electric motor and a gear housing in the speed reduction mechanism, a circuit case separate from both the housings, and the circuit case houses the control device. In Patent Document 1, a rotatable shaft in the electric motor and a worm shaft are connected to each other via a coupling having a spline, and the coupling is arranged in close proximity to the control device.
In the electric power steering apparatus discussed in Patent Document 2, a motor case in the electric motor includes a case on the motor main body side and a case on the substrate side connected to a gear housing, and a controller accommodation chamber is defined between the case on the substrate side and the gear housing.
In the electric power steering apparatus discussed in Patent Document 3, a common case is interposed between a motor housing and a gear housing. A motor chamber is defined between the case and the motor housing, and a controller accommodation chamber is defined between the case and the gear housing. In Patent Document 3, a rotatable shaft in the electric motor and a worm shaft are connected to each other via a torque limiter, and the torque limiter is arranged in close proximity to the control device. A bearing that supports the worm shaft, for example, is arranged in close proximity to the control device in addition to the coupling and the torque limiter.    [Patent Document 1] JP 2002-120739 A    [Patent Document 2] JP 2004-135492 A    [Patent Document 3] JP 2000-190856 A    [Patent Document 4] WO99/16654 Pamphlet    [Patent Document 5] JP 2002-345211 A    [Patent Document 6] JP 7-137644 A